Refining of mineral oils



O'ct- 1943- E. \c. HERMANN 2,332,793

REFINING OF MINERAL OILS Filed NOV. 30, 1940 Patented Oct. 26, 1943REFININ'G or MINERAIIOILS Eugene C. Hermann, Westfield, N. J assignorto, Standard Oil Developmentcompany, a corporation of DelawareApplication November 20, 1940, Serial No. 367,907

The present invention relates to the refining of mineral oils. Theinvention is more particularly concerned with the refining of petroleumoils boiling in the motor fuel, kerosene, and gas oil boiling ranges,and especially relates to an improved process for the removal ofobjectionable compounds therefrom, when utilizing as a treating agent amineral acid such as a sulfuric or an equivalent acid. In accordancewith the present process, acid treated oils, after the removal of theacid sludge, are subjected in an initial stage to a weak acid treatment,and then treated in the secondary stage with a washing solution whichpreferably comprises water. In accordanc with the preferred modificationof the invention, the treated oil isthen neutralized with a suitablealkali, as for example an aqueous caustic solution in order to producean improved refined product. t

It is well known in the art to refine mineral oils, particularlypetroleum oils, by various procedures involving distillation, acidtreating, clay treating, and neutralization stages. For example, itiswell known in the art to remove objectionable sulfur and relatedcompounds from petroleum oils, particularly from those petroleum oilsboiling in the motor fuel boiling range, by "treating the same withsuitable mineral acids. The spent acid solution is removed from the oilwhich is then washed in orderto remove free acidic constituents. The oilafter removal of the washing solvent is completely neutralized bytreating the same with an alkali metal treating agent such as an aqueoussolution of sodium hydroxide. In these operations the mineral acidusually comprises an acid of sulfur, particularly sulfuric acids ofvarious concentrations. The acid jtreating operation is usuallyconducted under conditions to secure a maximum removal of theobjectionable sulfur compounds and a minimum degradation'of the valuablepetroleum oil constituents furic acid. However the acid oil doescontain,

small quantities of acidic particlesuaswellas .small quantities ofsludge particles. In addition,

the oil alsofcontains various dissolved sulphonic acid constituents.

In order to remove these materials it has been the practice to treat theacid oil in one or more stages with a washing solution which usuallycomprises water. The separated aqueous layer 1 is acidic in nature andcontains all of the sulfuric acid constituents and the sludge particles.This acidic aqueous layer also contains someof the sulphonic acidconstituents clue tothe fact that these constituents are soluble in acidsolutions. However these sulfonic acid constituents arenot soluble inwater. As a result these sulfonic constituents are incompletely removedin conventional operations. This results in operating difiiculties sincethe water washed oil in order to completely free the oil of acid andrelated harmful constituents, is subsequently neutralized with asuitable alkali which usually comprises an aqueous solution of an alkalimetal hydroxide. This operation, while producing a product of highquality entirely suitable for utilization in internal combustion enginesand the like, does have the disadvantage that the sul' phonic acidconstituents react with the alkali to produce sulphonates, whichmaterials act as emulsifying agents, which produce emulsions which arediflicult to break.

These difficulties cannot be readily overcome sinceif a relatively largequantity of water or equivalent'solvent be utilized for the completeremoval of the deleterious sulfuric acid and sludge constituents fromthe acid oil the resulting solution is relatively weak with respect toits acidity andincomplete removal of the sulfonic acid constituents fromthe oil results. On the other hand'if a relatively small volume of wateris employed for treating the acid oil, the acidity is satisfactory withrespect to the solvency of the sulfonic acid constituents but incompleteremoval of the sulfuric acid and sludge constituents re sults.Furthermore, when employing-a relatively small volume of water pervolume of acid oil an appreciable carry-over of undesirable constituentsis experienced.

. Ihave now discovered a process by which it is .possible to removeobjectionable sulfur and related compounds from mineral oils utilizing amineral acid, and to completely neutralize the same in an, efficientandeconomical manner. In

accordance with my process, the mineral or pe initial stage with adefinite amount of waterunder conditions in which the oil is subjectedto a dilute sulfuric acid solution having a. definite concentration. Ihave found that if thi operation be conducted, substantially the entireamount of undesirable sulphonic acid constituents are removed with theweak acid solution. These constituents thus are not able to subsequentlyreact with the alkali which cause undesirable emulsions which increasethe consumption of the alkali to produce sulphonates. The treated oil,after removal of the weak acid solution, is then subjected in asecondary stage to a treatment with a sumcient quantity of water whichis *trations, may vary widely.

able for the refining of petroleum oils boiling in the motor fuel andlight gas oil boiling range, with which neutralized sulphonic acidconstituents function to produce aqueou emulsions in the neutralizationstage. 5

Temperature and pressure conditions of the acid treating operation, aswell as acid concen- In general, atmospheric temperatures and pressuresare employed,

adjusted to substantially completely remove the remaining sulphuric acidconstituents. This oil is then removed and completely neutralized bytreatment with a suitable alkali metal hydroxide solution to produce afinished product having'an exceptionally high quality. A,

The process of my invention may be readily understood by reference tothe attached drawing illustrating modifications of the same. Forpurposes of description it is assumed that the feed oil comprises acracked distillate boiling in the motor fuel boilin range which containsdissolved therein bjectionable sulfur compounds, as for examplemercaptans and related sulfur compounds. This oil is introduced intoacid treating mixing zone] by means of. feed line 2 in which it iscontacted witha suitable acid, which for the purpose of description istaken to'be sulphuric acid. The. sulfuric'aci'd is introduced into thesystem by means of line 3. It is to be understood that treating zone Imay comprise a series of batch units, or may comprise any number ofcountercurrent'acid treating stages. The acid oil is withdrawn from acidtreating zone I by means of line 4 and passed serially through settlin'gzones 5 and 6. Acid sludge containing the undesirable sulfurconstituents is'withdrawn from the respective units by means of line 1and 8. The acid oil is withdrawn from settling unit 6 by means of line 9and mixed with a weak acidic so,- lution which-is introduced by'means ofline l0. The'mixture is passed'to settling zone H from which the weakacid layer, containing dissolved therein sulph'onic acid constituents,is withdrawn by means of line I2. The oil layer, completely free ofsulphonic acid constituents, is withdrawn from settling zone II by meansof line l3 and mixed with a quantity of water, which is introduced bymeans'of line 14. This mixture is introduc'ed :into settle zone I5 fromwhich the water solution containing dissolved therein'sulfuric acidconstituents and sludge particles, is removed by mean of line I 6. Thetreated oil is then removed from settling zone l5 b'y'means of line Hand completely sweetened by mixing with a neutralizing agent which istaken to be a sodium hydroxide solution which is introduced into thesystem by means of line l8. The mixture is intr'oducedinto settling zoneI9 from which the spent sodium hydroxide solution is Withdrawn bymeans/of line 20, while the treated oil is withdrawn by means of-line2|.

The process of the present invention may be widely varied. The inventionessentially comprises subjecting an acid treated oil, after removal ofthe acid sludge, to a weak acid wash prior to removing the treated acidconstituents from the same. I

The invention may be applied in the treatment of any petroleum oil whichis refined by the treatment of a sulfuric or an equivalent acid such asan acid or phosphorus and the like However,

although temperatures in the range below 40 F. to F. andthe' like arealso suitable. The acid concentration will depend upon the particularacid'us'ed, the quantity of acid used, th type of feed oil beingtreated, and the character and con centration of the undesirable sulfurcompounds.

In general acid concentrations vary in the range from-about 40% tofuming acids and the amount of acid varies in the range from about 1 lb.to about 30 lbs. of acid per barrel of oil being treated.

The acid oil after separation of the acid sludge is treated with aquantity of weak acid solution which is adjusted in a manner that theacid concentration is in the rangefrom about 0.5 to 3.0% strength,preferably about 1.5 to 2.5% strength. Under certain conditions,providing thequan'tity of water added to the initial stage be relativelylow, the amount of acid remaining in the acid oil will be sufiicient tosecure this concentration. For example, we have discovered that whentreat ing a petroleum oil boiling in the motor fuel boiling range with 5to 15 lbs. of to 98% of sulfuric acid if l to 5 volumes of water pervolume of oil be added in the initial stage, the acid concentration inthe oil will be in the range from about 0.5 to 3.0%. g'

The amount of water addedrin the secondary stage is adjusted in a mannerto completely remove the sulfuric acid constituents; The amount ofneutralizing agent likewise is adjusted in order to completelyneutralize'all remaining acid constituents. 1

In order to further illustrate the invention, the following example isgiven which should not be construed as limiting the same in any mannerwhatsoever.

Example Various operations were conducted to determine the solubility ofsulphonic acids with the following results: I

. Per cent water in mix of 8.6 10.2 15.9.

oil and Water. Methyl orange acidity of 12.2 8.7 6.9.

water phase as cc.s of N/10/5 cc.'s. Nature of water phasc Sulphonic V er y Incomplete acids well slightly solution of dissolved. murky.sulphonic acids. Sp. gr. of water phase".-. 1.0233 l.0l98 1.0165.

about 3.0% in an initial stage, separating the oil from the dilute acidsolution and washing the oil in a secondary stage with water.

2. Process in accordance with claim 1 in which said mineral oil is apetroleum oil boiling in the motor fuel boiling range. a

3. Process for the production of a refined oil product from a feed oilcontaining objectionable sulfur compounds which comprises contactingsaid feed oil with sulfuric acid under conditions to form an acid sludgecontaining the objectionable sulfur compounds, separating the acidsludge from the oil, treating the oil in an initial stage with an addeddilute sulfuric acid solution having a concentration in the range fromabout 0.5% to about 3.0%, separating the dilute sulfuric acid solutionand. treating the oil in the secondary stage with water, separating thewater, contacting the oil in a tertiary stage with an alkali metalhydroxide solution and separating the treated oil product.

4. Process in accordance with claim 3 in which said petroleum oil boilsin the motor fuel boiling range.

EUGENE C. HERMANN.

